End-game Guide (Spoilers!)

[LitmusDragon]

This is a quick guide for the Xantos encounter, and for the post-game options that open up after you beat him. Don't read on if you want to be surprised.

Updated 04/24/2014 for game version 1.12!

XANTOS STRATEGY:

Xantos is a level 102 "Strange Being" with 20,000 HP. He has a fairly average deflect value, so it's possible to deal fairly good melee damage against him. He has 75 to all resistances, so spell damage is also fairly effective. Xantos can cast spells from all 6 schools, and is smarter about spell casting than the other monsters in the game, using only the best spells of each school. He also has a special attack called "Anti-matter" which deals 250-350 damage and is not reduced by resistances. He is a vampire type monster, and unlike other vampire type monsters, he regains the full amount of damage per hit as healing whenever he attacks.

You can not flee from this encounter (the reason will be obvious once battle starts), so make sure you have applied all of your boons and your HP is at full before you confront him. Xantos will appear on level 99 in a similar spot to where the stairs appear on other levels.

It's strongly recommended to have a maximized Trade before you attempt him, and in the case of Archaeology, that you have your Trade weapon. Also, all of your resistances (except Poison) should be close to 95.

For physical damage classes (classes that use Attack primarily) you will need a lot of healing potions to make it through the encounter. As a general rule, at least 15 or 20. Suggestion: map these to a function key. Celerity potion is a must I think, plus all 6 scrolls, and Lucky, stat potion, and a Frothing potion. Xantos does not attack as often as he casts spells, so the drawback from the Frothing potion is negligible.

For spell casting classes, you will need a mix of Healing and Mana potions. Kinetic potion is an absolute must, along with Sage's, Celerity, whatever Boons your class can cast, and whatever scrolls are useful to you as boons. In general, Storm is the most damaging spell against him, though it can be unpredictable. Charged Blast is fairly effective if you don't want to waste gems. As a Mage, I would strongly suggest the Scholar profession, as it's level 99 ability is quite powerful.

Xantos takes about 100 turns to defeat.

If you die fighting Xantos, you will respawn in town. You will not be penalized any gold and the maps will not reset.

You can fight Xantos multiple times and the game will track your best time (fewest number of turns beating him). Once you beat him you're presented with a screen stating the number of turns and whether it was your best time or not.

POST GAME:

Once you beat Xantos, you will be presented with a "cast of characters" scrolling credits screen that lists all of the monsters you've encountered in the game, and all the monsters you haven't yet encountered.

After beating Xantos, additional options open up in the System menu: "Reply Credits" and "Teleport to Dungeon Level". These options allow for a completely optional post-game of trying to complete the "% of creatures encountered" stat. Can you encounter every monster in Endless Dungeons? It would be quite a challenge!

IF YOU JUST WANT TO SEE THE XANTOS ENCOUNTER:
I made a Youtube video: https://www.youtube.com/watch?v=pYIl8eLHZdo